How much should my system generate?

Solar generation changes a lot through the year. A system that makes plenty in June can make very little in December, and that's normal. Here's how to tell whether yours is doing what it should.

A typical year

In England, each kWp of panels facing south makes very roughly 850 to 1,100 kWh a year, more in the south and less in the north. East or west roofs, steeper or flatter roofs, and shading all bring that down.

This is how a south-facing system in the Midlands spreads its year, from the EU's PVGIS solar calculator:

So April to September makes about two thirds of the year's electricity, and November to January only about a tenth. A December day can easily be a fifth of a June day, or less.

Compare like with like

• Compare the same month last year, not winter with summer. Your app can show monthly and yearly totals.
• Compare a whole month, not one day. A single dull day can make a tenth of a bright one.
• Your neighbour's system may face a different way, have more panels or be shaded differently.

Why the app and your meter may not match

Your app reads from the inverter, and your electricity meter measures in a different place, so small differences are normal. Some apps also count battery output in their totals, which can make figures look higher than what the panels made.

Things that lower generation

• Short days and low sun in winter, cloud, and snow on the panels.
• New shading from a tree that has grown, scaffolding or a new building.
• Heavy dirt, moss or bird droppings that rain isn't shifting. See Solar Panel Maintenance & Cleaning FAQs.

When to contact us

• Generation drops suddenly, on sunny days, and it isn't the weather.
• Your yearly total is well below last year's with similar weather.
• There's an alarm or error on the inverter or in the app.
• The app shows nothing at all: check My system isn't generating first.